Archives For
Ecology & Wildlife

The Chicago Botanic Garden is actively maintaining, restoring, and recreating four natural areas at the Garden: woodlands at McDonald Woods and the Brown Nature Reserve, the Dixon Prairie, the Skokie River Corridor, and the 60-acre Garden Lakes. These activities teach restoration ecologists a great deal about habitat management, which can be applied in other regions.

Senior ecologist Jim Steffen describes his close encounters with curious and beautiful bats.

A few years ago, in early spring, I was traveling through McDonald Woods at the Chicago Botanic Garden, searching for some of the flat-bodied crab spiders (Philodromus) that typically spend the winter in communal groupings under the loose bark of dead trees. Upon reaching a small stand of dead American elm trees, I began to lift the loose remaining bark away from one of the trees to see if any spiders were present.

As I gently pulled the bark away from the trunk, a tiny black hand reached up over the top edge of the bark. It quickly became obvious that there were more than spiders under this bark!

Although I was a little startled to have this hand slowly reach out in front of my face, I immediately realized that this piece of loose bark was the day roost of a silver-haired bat. The silver-haired bat is a medium-sized bat that is a dark chocolate brown or black with white hairs scattered among the dark hairs on its back. I gently released the bark so as not to disturb the napping bat any more than I already had. This is just one example of why it is important to maintain at least some dead standing trees in our woodland communities.

A silver-haired bat curls up tightly on a tree in McDonald woods. Photo by Jim Steffen

Even though bats are fairly common mammals in our area, since they are almost totally nocturnal, we don’t get to see them all that often—especially at close range, when we would be able to admire their delicate form and attractive appearance. Bats are in the order Chiroptera, roughly translated as “hand wing,” and are the only mammals that are actually capable of true flight (unlike flying squirrels—which we also have at the Garden).

You might be familiar with another group of small mammals known as shrews. Shrews are mouse-like animals that are actually carnivores that feed heavily on invertebrate populations. Although bats may have varied diets around the world, here they are primarily insect eaters, much like shrews with wings.

When I was in college studying mammology, we used to go out at night and look for streetlights where there were large numbers of moths and other flying insects attracted to the lights. We would then take out our car keys and jangle them around to make high-pitched sounds with the keys clinking together. These high-pitched sounds would simulate the high-pitched sounds produced by the echolocation sounds produced by hunting bats to locate their prey. (Unless we are equipped with special listening devices, we are not able to hear the sound of bat echolocation.) Often times, many of the moths would begin flying erratically, or drop out of the air as though they had been struck with a stupefying charm from Harry Potter’s wand. These moths have evolved defensive tactics to help them avoid being eaten by bats by flying in erratic patterns or closing their wings and dropping if they heard the sounds of an approaching bat.

An eastern red bat (Lasiurus borealis) clings to black landscape fabric at the back of one of the buildings here at the Garden. Photo by Jim Steffen

Many years later, while removing invasive garlic mustard from our oak woodland a few summers ago, I came upon an oak tree with a broken branch. All of the leaves on the branch had turned a bright reddish-brown that stood out against the backdrop of all the other green foliage. On closer examination of the branch, I spotted a female eastern red bat hanging upside down, in typical bat fashion, with its single offspring clinging to it. I don’t know if the bat was aware of it, but this dead branch provided the perfect camouflage for her rich color.

This made me think about how these mammals perceive the world. Do bats have color vision, and was this red bat able to tell that the dead branch would be such a good match for its own color? Most nocturnal animals tend not to have color vision, since color does them little good in the dark. Most bats are various shades of brown, black, or gray. (It is a different story for birds that are mostly active during the day and use bright colors as a means of attracting mates or advertising territories.)

We have five species of bats that are likely to be seen at the Garden. Some of them are summer residents, like the little brown, big brown, and eastern red bat, while others are mostly migratory species, like the silver-haired and hoary bats that show up during their spring and fall migrations. Years ago, in the late fall, while using fine nets at night to capture owls for attaching U.S. Fish and Wildlife Service bird bands, I often caught many of the large, hoary bats migrating south for the winter. These large bats have an attractive frosted appearance with a mix of white and reddish hairs all over their bodies.

While I was studying birds in the tropical rain forest of Central America, I often encountered small colonies of bats hanging at eye-level, under the broad leaves of Heliconia plants. I think these wide, tent-like leaves were chosen mostly for the protection they gave the bats from the torrential downpours that occurred every day. However, the bats we find here are either solitary animals, like the red, silver-haired, and hoary bats that live solitary lives in the woodlands and forests, or they are colony-forming bats, like the little and big brown bats, that search out attics, barns, or large hollow trees where they gather in groups to raise their young.

Some of the bat species also search out caves or old mine shafts during the wintertime, where the subterranean habitat provides moist, stable conditions with above-freezing temperatures suitable for hibernation. It is possible to construct bat houses that, if placed in the proper locations, can attract and support colony-forming bats during the summer.

We have several of these bat house installed on buildings around the Garden. This summer, one of those houses contained half a dozen bats—probably little browns. It is best to place bat houses in full sunlight, since the bats have high body metabolisms and prefer very warm conditions for roosting during the summer. Think you’d like to build a bat house? Construction details can be found at the Bat Conservation International website at batcon.org.

Another local flier, this very tame flying squirrel enjoyed a snack of walnut with his photo op. Photo by Jim Steffen

Bats are more than curious and beautiful creatures; they are also tremendously important components of a healthy environment. They are extremely important control agents of insect populations. Many of the insect species they eat are harmful crop pests, like army cutworm, or irritating or disease-carrying species like mosquitoes. Some bats can consume more than 1,000 mosquitoes in a single night! Bats are in trouble now for many reasons—not the least of which are climate change, exotic diseases like white-nose syndrome, and habitat loss.

Although bats are seldom seen and often have scary, erroneous wives-tales associated with them, we should be working hard to correct the problems that might lead to a truly silent night.

For example, you might find stream bluets along the river and orange bluets hanging out on the lily pads. Most species measure about an inch in length and can be easily overlooked, but when you take time to slow down and search for these tiny gems, you will be rewarded with finding some of nature’s most beautiful hunters. Indeed, these tiny insects are fierce hunters—but don’t worry, as they neither bite nor sting humans. Their preferred food choice is other, smaller insects (including mosquitoes).

The main differences between dragonflies and damselflies are their size and wing positions. Damselflies, in general, are smaller, and hold their wings over their abdomens. Dragonflies tend to be larger, with a heavier body, and hold their wings out to the side.

The most common species around here is the eastern forktail damselfly. Identifying them can be tricky, as they come in several different varieties! The males and females look very different from each other, and the females change color as they age.

I like to get out early in the morning. The light is low, there is often dew, and the insects move a bit more slowly until they warm up. One of my favorite places in the Garden to photograph damselflies is in the Dixon Prairie. They like to hang out on the grasses there. Walking slowly on the path next to the plants, you will see what look like tiny flying sticks. Damselflies will often congregate in one area and, if disturbed, sometimes land just a short distance away. I like to use my 105mm or 200mm macro lenses to photograph these beauties. They will fly until the first really hard frost. There are dozens of species native to this area—all of them beautiful and fierce hunters.

One of our favorite insects at the Chicago Botanic Garden is the praying mantis. So we were very excited to obtain an egg case earlier this spring. We decided to keep it indoors so we could watch it hatch, and then release the newly hatched insects into the Garden.

About 100 praying mantises emerged from this ootheca and were released into the Grunsfeld Children’s Growing Garden.

A praying mantis egg case is called an ootheca (pronouned oh-uh-THEE-kuh). The plural is oothecae (oh-uh-THEE-see). The ootheca was produced by a female praying mantis last fall. She laid her eggs in this foam of protein that hardened around a stick and protected the eggs through the winter. The eggs usually hatch in mid-June to early July. The half-inch-long immature praying mantis nymphs resemble the adult, but they do not have wings.

Colorless praying mantis nymphs emerge from the ootheca all at one time. During their first hour, they darken in color to blend in with their surroundings.

After our praying mantises hatched inside an insect cage, I discovered that a bed of false sunflower plants (Heliopsis helianthoides) in the Grunsfeld Children’s Growing Garden was infested with red aphids. I released the praying mantises, and the hungry babies immediately began to feed.

At first, the praying mantis babies seemed a little bewildered by their new surroundings, but they quickly acclimated.

This mantis held very still as it eyed its prey.

These four little mantises lined up and stared at the aphids that would certainly become lunch soon.

It wasn’t exactly aphid carnage—much to the disappointment of our eighth grade Camp CBG helper, Joshua, who assisted me with the release—but the young predators did appear to enjoy their first meal.

By the end of August, some of our little friends will be as big as this praying mantis (and just as hungry)!

It may surprise you to know that although it looked like a bad infestation, aphids are not really a big problem for the plants. When they are very abundant, it does not take long for natural predators like praying mantises and ladybugs to find them and move in for a feast. Predatory insects will take care of the problem if you are patient and let nature take its course. If aphids show up in your garden and they bother you, we recommend hosing them off with water rather than using an insecticide, because chances are pretty good that there are beneficial insects on your plants, too. Hosing with a strong jet of water will knock off all the bugs and kill most of the aphids, but it won’t be as devastating to the mantises or other beneficial insects as poison.

We have placed praying mantis oothecae in the Regenstein Fruit & Vegetable Garden and Elizabeth Hubert Malott Japanese Garden, as well as in the Children’s Growing Garden, to ensure that there will be a population of our favorite insect for you to find. Many of them will survive on aphids and other insects they capture and devour on our flowers, and they will grow up over the summer. The next time you visit, stop by and see if you can find them helping our plants remain healthy and less bothered by pests.

Monarch butterflies have left their overwintering sites in Mexico and are heading back toward the Midwest, including the Chicago area.

Unfortunately, far fewer monarchs will be making the northward flight this year and the chance to see large numbers of these beautiful butterflies in your garden or flying across a prairie is becoming less certain.

Butterfly weed (Asclepias tuberosa) is one of many native milkweed species that provide food for monarch butterfly caterpillars and a nectar source for flower visitors such as bees and butterflies.

In the 1990s, hundreds of millions of monarchs made the journey each fall from the northern plains of the United States and Canada to forested sites north of Mexico City. In western North America, more than a million monarchs made a shorter flight to tree groves on California’s coast. However, monarch numbers have been declining for more than a decade, and this year scientists documented record low numbers. We have seen more than a 90 percent decline.

Why is this occurring? We don’t know for sure, although there are several factors that are likely contributing. Habitat loss due to urban development and large-scale agriculture are key concerns. Farms now cover vast areas and many grow genetically modified crops that allow herbicide applications to be used on and around the crop, including in areas where milkweed—the one plant that monarch caterpillars need—used to grow. These “Roundup ready” crops have been identified as a major cause of milkweed loss throughout the Midwest. Additionally, millions of acres of farms and urban land are treated with toxic insecticides. The loss of forest habitat in Mexico and the decline of monarch groves in California may also be playing a role. In the West, severe drought is likely contributing to reduced monarch populations. These threats are compounded by climate change.

We do not have to sit and watch these declines continue.

We can provide these butterflies (and other wildlife) with high-quality, insecticide-free habitats. This is not something that needs to be restricted to a distant wilderness. Indeed, it is a cause in which everyone can take part. Homeowners and farmers can plant milkweed to support monarch caterpillars, and native flowers to provide nectar for adult butterflies, and work to limit the impact of insecticides. Land managers can ensure that milkweed stands are adequately protected.

The Milkweed Seed Finder gives you quick access to regionally appropriate seed sources, with options to search by milkweed species and by state.

The Xerces Society’s Project Milkweed has been working with native wildflower seed nurseries, the USDA Natural Resources Conservation Service (NRCS), and community partners to produce huge volumes of milkweed seed that are being used to restore monarch habitat. In just three years, this work has led to the production of 35 million milkweed seeds! As a result of this effort, milkweed seed is rapidly becoming more available in many regions of the country. To make it easier for people to find seed sources, we’ve launched the Milkweed Seed Finder, a comprehensive directory of milkweed seed vendors across the country.

In addition, the Xerces Society’s work with farmers and the NRCS has led to the creation of tens of thousands of acres of wildflower habitat that includes milkweed, across much of the monarch’s breeding range.

Aldo Leopold wrote in A Sand County Almanac, “One of the penalties of an ecological education is that one lives alone in a world of wounds.” For the sake of the monarch—and so many other species—it is time to heal as many wounds as possible.

I have to admit, I’ve never heard such spring peeping at the Chicago Botanic Garden before. But last weekend, as I enjoyed several long walks here (including one with my sons on Mother’s Day at 6:45 a.m.!), I felt serenaded by a loud chorus of frogs and toads. (Some visitors are even mistaking the sound for chirping birds.)

Working off the hypothesis that the Garden’s shoreline restoration efforts have helped increase frog and toad populations here, I turned to Garden scientists for answers.

And this is what I learned: of the Garden’s 385 acres, nearly one-quarter (81 acres) is water. More than three-fourths of the Garden’s shoreline has been restored since 1999, addressing long-standing erosion problems. Most recently, the Garden restored 1¼ miles of shoreline around the North Lake; the ten-month project was completed in summer 2012. As part of the project, we added more than 120,000 native plants—the largest perennial planting project in the Garden’s history—to stabilize shoreline soil. The sturdy plants, some with roots more than 6 feet deep, resist erosion and enhance water quality by filtering eroded soil and excess nutrients. The renovated shoreline provides an enhanced habitat for our aquatic life, which includes wood ducks, double-crested cormorants, and snapping turtles, along with bullfrogs, American toads, and other members of their croaking chorus. Build a healthy habitat and they will come!

Adding to the cacophony is an even bigger chorus than usual because of our “compressed” spring this year. Usually, the frogs emerge first, followed by the toads. This May, the frogs and toads are singing together—but not for long; come to the Garden soon if you want to hear them.

Abloom in May, native plants and sedge create habitat, protect shorelines, and create a beautiful border around the North Lake.

Even if you miss hearing them, I encourage you to listen to the short audio clip above and think about frogs (at least for a few seconds). Sometimes, we overlook the humble frog in favor of the more romantic songbirds in spring. In popular culture, the frog tends to fare better in other parts of the world. In Japan, for instance, the frog is considered a symbol of good luck. The Japanese word for frog is kaeru, which also means “to return.”

When I hear the frogs at the Garden from now on, I will think about how their return, spring after spring, announces that they’ve come home. I am proud that our conservation actions here have given them a healthy habitat in which to thrive, and I feel grateful to the frogs for giving me a moment to reflect on the importance of the Garden’s mission: We cultivate the power of plants to sustain and enrich life.